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40 lines
2.3 KiB
ReStructuredText
40 lines
2.3 KiB
ReStructuredText
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Object Serialization
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====================
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What is serialization (and deserialization)?
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--------------------------------------------
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Object serialization is the process of converting objects into a stream of bytes and, deserialization, the reverse
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process of creating objects from a stream of bytes. It takes place every time nodes pass objects to each other as
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messages, when objects are sent to or from RPC clients from the node, and when we store transactions in the database.
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Whitelisting
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------------
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In classic Java serialization, any class on the JVM classpath can be deserialized. This has shown to be a source of exploits
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and vulnerabilities by exploiting the large set of 3rd party libraries on the classpath as part of the dependencies of
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a JVM application and a carefully crafted stream of bytes to be deserialized. In Corda, we prevent just any class from
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being deserialized (and pro-actively during serialization) by insisting that each object's class belongs on a whitelist
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of allowed classes.
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Classes get onto the whitelist via one of three mechanisms:
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#. Via the ``@CordaSerializable`` annotation. In order to whitelist a class, this annotation can be present on the
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class itself, on any of the super classes or on any interface implemented by the class or super classes or any
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interface extended by an interface implemented by the class or superclasses.
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#. By returning the class as part of a plugin via the method ``customizeSerialization``. It's important to return
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true from this method if you override it, otherwise the plugin will be excluded. See :doc:`corda-plugins`.
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#. Via the built in Corda whitelist (see the class ``DefaultWhitelist``). Whilst this is not user editable, it does list
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common JDK classes that have been whitelisted for your convenience.
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The annotation is the preferred method for whitelisting. An example is shown in :doc:`tutorial-clientrpc-api`.
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It's reproduced here as an example of both ways you can do this for a couple of example classes.
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.. literalinclude:: example-code/src/main/kotlin/net/corda/docs/ClientRpcTutorial.kt
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:language: kotlin
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:start-after: START 7
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:end-before: END 7
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.. note:: Several of the core interfaces at the heart of Corda are already annotated and so any classes that implement
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them will automatically be whitelisted. This includes `Contract`, `ContractState` and `CommandData`.
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